1. Field of the Invention
The present invention relates to a pneumatic tire, and more specifically to a pneumatic tire excellent in wear resistance in summer (including spring and autumn) without deteriorating steerability and heat durability and further in drivability, braking ability and steerability on icy and snowy roads in winter. In addition, the present invention relates in particular to a pneumatic tire which can improve riding comfortability and road noise and further anticrack resistance at tire groove bottoms. This application relates to a copending application which was filed on Jan. 30, 1987 and bears U.S. Ser. No. 009,367.
2. Description of the Prior Art
In general, studless tires and foam rubber tires having foam rubber on the tread are used to prevent dust pollution and road damage as all-season tires suitable for use in travelling both on icy and snowy roads in winter and on paved roads in summer.
Prior-art pneumatic tire using foam rubber on the tread, is a so-called block pattern such that the tread is formed with blocks partitioned by circumferential and lateral grooves or a so-called lug pattern such that the tread is formed with lateral grooves has been well known. These prior-art pneumatic tires are provided with certain tire performance on icy and snowy roads in winter season. However, there still exists a problem in that since circumferential driving forces, circumferential braking forces and lateral forces are repeatedly applied to both tread side areas during travelling, and therefore dynamic strains are repeatedly concentrated at groove bottoms of the foam rubber, cracks are produced at groove bottoms.